Correlation Between FMIN(Frequency Minimum) and LOF(Lowest Observed Frequency),

Synoptic maps of a normalized function of fmin are used to obtain the integrated absorption along a 10,000 km propagation path for comparison with the lowest observed frequency LOF measured by oblique incidence ionosonde over the same path in the month of July 1966. With the integrated absorption represented by a linear summation of normalized fmin at equally spaced points along the path, cross-correlation with LOF for the whole month yields a coefficient of o.6. Alternative methods of performing the integration of absoption along the path may improve this correlation, so that oblique absorption can be predicted from vertical measurements of fmin. AUthor